In copending U.S. patent application Ser. No. 12/975,805 filed Dec. 22, 2010 (US Patent Publication No. 2011-0165314 published Jul. 7, 2011), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described the preparation of a clean tasting, non-beany soy protein product that has a near neutral natural pH and can replace conventional soy protein isolate products in various food applications including nutritional bars, baked goods and processed meat products. Patent application Ser. No. 12/975,805 also demonstrated that the functional properties of the soy protein product may be modified, with the protein solubility reduced and the water binding capacity increased by including a heat treatment step in the preparation of the product.
Such soy protein product is derived from the novel soy protein product described in U.S. patent application Ser. No. 12/603,087 filed Oct. 21, 2009 (US Patent Publication No. 2010-0098818 published Apr. 22, 2010) and Ser. No. 12/923,897 filed Oct. 13, 2010 (US Publication No. 2011-0038993 published Feb. 17, 2011), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference. U.S. patent application Ser. Nos. 12/603,087 and 12/923,897 describe the production of a novel soy protein product, preferably an isolate that produces transparent and heat stable solutions at low pH and, therefore, may be used for protein fortification of, in particular, soft drinks and sports drinks, as well as other aqueous systems, without precipitation of protein.
The soy protein product produced therein has a unique combination of parameters not found in other soy protein isolates. The product is completely soluble at acid pH values of less than about 4.4 and solutions thereof are heat stable in this pH range, permitting thermal processing, such as hot fill applications. No stabilizers or other additives are necessary to maintain the protein in solution or suspension. The soy protein solution has no “beany” flavour and no off odours. The product is low in phytic acid and no enzymes are required in the production of the soy protein product. The soy protein product is also highly soluble at about pH 7.
The novel soy protein product having a soy protein content of at least about 60 wt % (N×6.25) on a dry weight basis (d.b.), preferably an isolate having a protein content of at least about 90 wt %, is produced by a method which comprises:                (a) extracting a soy protein source with an aqueous calcium salt solution, particularly calcium chloride solution, to cause solubilization of soy protein from the protein source and to form an aqueous soy protein solution,        (b) separating the aqueous soy protein solution from residual soy protein source,        (c) optionally diluting the aqueous soy protein solution,        (d) adjusting the pH of the aqueous soy protein solution to a pH of about 1.5 to about 4.4, preferably about 2 to about 4, to produce an acidified clear soy protein solution,        (e) optionally heat treating the acidified solution to reduce the activity of anti-nutritional trypsin inhibitors and the microbial load,        (f) optionally concentrating the aqueous clear soy protein solution while maintaining the ionic strength substantially constant by using a selective membrane technique,        (g) optionally diafiltering the concentrated soy protein solution,        (h) optionally pasteurizing the concentrated soy protein solution to reduce the microbial load, and        (i) optionally drying the concentrated soy protein solution.        
In copending U.S. patent application Ser. No. 12/704,078 filed Feb. 11, 2010 (US Patent Publication No. 2010-0203205 published Aug. 12, 2010), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described the production of a soy protein product (termed “S702”) having comparable properties to the soy protein product provided in accordance with U.S. application Ser. Nos. 12/603,087 and 12/923,897. In application Ser. No. 12/704,078, the soy protein product is produced by extracting soy protein source material with an aqueous calcium salt solution to cause solubilization of soy protein from the protein source and to form an aqueous soy protein solution, separating the aqueous soy protein solution from residual soy protein source, concentrating the aqueous soy protein solution while maintaining the ionic strength substantially constant by using a selective membrane technique, optionally diafiltering the concentrated soy protein solution, and drying the concentrated soy protein solution.
In copending U.S. patent application Ser. No. 12/703,996 filed Mar. 4, 2010 (US Patent Publication No. 2010-0203204 published Aug. 12, 2010), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described the production of a soy protein product (termed “S7300”) having comparable properties to the soy protein product provided in accordance with U.S. Ser. Nos. 12/603,087 and 12/923,897. In application Ser. No. 12/703,996, the soy protein product is produced by extracting a soy protein source material with aqueous calcium chloride solution to cause solubilization of soy protein from the protein source and to form an aqueous soy protein solution, separating the aqueous soy protein solution from residual soy protein source, concentrating the aqueous soy protein solution while maintaining the ionic strength substantially constant by using a selective membrane technique, optionally diafiltering the concentrated soy protein solution, diluting the concentrated and optionally diafiltered soy protein solution into water to cause the formation of a precipitate, separating the precipitate from the diluting water, and drying the separated soy protein precipitate.
In copending U.S. patent application Ser. No. 12/693,714 filed Jan. 26, 2010 (US Patent Publication No. 2010-0189853, published Jul. 29, 2010), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described the provision of a soy protein product (termed “S200Ca”) having comparable properties to the soy protein product provided in accordance with U.S. Ser. Nos. 12/603,087 and 12/923,897. In application Ser. No. 12/693,714, a calcium salt is added to supernatant from the precipitation of a protein micellar mass to provide a solution having a conductivity of about 2 mS to about 30 mS, removing precipitate from the resulting solution to leave a clear solution, optionally adjusting the pH of the clear solution to about 1.5 to about 4.4, concentrating the optionally pH-adjusted clear solution to a protein content of about 50 to about 400 g/L to provide a clear concentrated soy protein solution, optionally diafiltering the clear concentrated protein solution, and drying the concentrated solution.